Price wise...check out some of the magazines like Shotgun Review, etc. to see what AR's are going for in different parts of the country. Keep in mind that buying on-line requires that you have the gun transferred to a local FFL dealer in your area, which usually requires a fee for his service. Another option is to go to a local gun show in your area. Gun shows often have some pretty decent deals and alot more variety than you might find in a local store. And if you work it right, you can sometimes get the price down to what is affordable for you.
As for manufacturers, like I said earlier, if you stay with a reputable brand, you should be okay. It used to be said that one should stick with the A,B,C's - Armalite, Bushmaster, Colt. One would still be safe with any of those 3, but there are so many new players in the market that shouldn't be disregarded either. DPMS, often gets a rap from folks for whatever reason, but none that I have found to be true or experienced in any of the 6 that I own. Not that 6 firearms is a true representation of their overall quality, but in my case, they were purchased over a 10 year span, and have had ZERO malfunctions of any sort. Stag is another new comer, making excellent quality pieces in right or left hand configurations, if that is something you might need. Rock River is also an excellent make, putting out some very nice pieces. I do like their firearms, but am not a total devotee as some. Yes, the fit between their receivers is tighter than almost anyone else in the field, and if that is what you need, then there it is. But some of the old timers will also tell you that is not necessarily a good thing at times either. Sabre Defense, LMT, CMMG, JP, Wilson Combat, Les Baer, the list goes on and increases daily. All are fine firearms, as long as you do your part, too, maintenance, ammunition selection, etc. Price wise, you can build one from a kit or put together a complete upper and complete lower for less than $700. Complete rifles usually start above that and can go as high as your wallet or second mortgage might allow. First decide what your price cap will be, then it makes it easier to decide on which way to go, even though it might be nice to have brand xyz's ultra-uber tacticool model. The nice thing about the AR is, you can save up the pennies to build even the most basic of models up into that ultra tactical model that you've always drooled about. All it takes is $$$ But to start, know that most of all the entry level AR's out there, again from a reputable manufacturer, will do what you want it to do.
My first AR was a Bushmaster that my wife actually bought for me as a X'mas/birthday/father's day gift a long time ago. I still own it, and it has never failed to go bang, even with 5000 rounds through it. It is joined in the safe by a few other Bushmasters, Armalites, Colts, DPMS, Rock River, Wilson, Stag, and quite a few that I have put together from parts. Sure, every now and then you run across a part that could have been machined a little better or the hole was a little tight, but nothing I have found so far that would indicate any kind of a trend by one manufacturer versus any of the others, and nothing that could not be easily remedied, or fixed/replaced by said reputable manufacturer.
By the way, not taking anything away from Rock River, but it is interesting to note in their catalog and site, yes the 20" NM with a NM trigger will shoot MOA or better. But their PRO series AR's that cost almost 2x more are only guaranteed to 1 1/2 MOA?? I'd have to go with the Les Baer, at least they GUARANTEE that their's will shoot 1/2 MOA.
Good luck on your choice and welcome to the world of AR's
